The present invention relates to tank pressure-control system, and particularly, to an apparatus for regulating discharge of liquid fuel and fuel vapor from a fuel tank. More particularly, the present invention relates to a tank venting control apparatus that closes quickly and automatically at the proper time to prevent discharge of agitated liquid fuel from the tank and overfill of the tank and that opens automatically at some point after fuel agitation has subsided or tank refueling has ended to vent the vapor space in the tank.
Some conventional buoyant float members of the type used in tank control valves are unable to react quickly enough to rising liquid fuel in the tank to move a tank closure valve to its vent-closing position in the tank. Often, a float member moves upwardly to urge the tank closure valve to a position closing a venting outlet in the tank only when a sufficient amount of liquid fuel in the tank is displaced by the float member. This displacement must generate enough buoyant force (to add to the lifting force generated by a compression spring acting on the bottom of the float member) to lift the float member upwardly to close the venting outlet in the fuel tank. Many conventional float members have somewhat open-ended bottom portions. These open-ended bottom portions do not displace a lot of liquid fuel when met with rising liquid fuel in a tank. Therefore, there might be a delay period between the time that such a conventional float member is first exposed to rising liquid fuel and the time that the float member begins to float and move a closure valve upwardly to its vent-closing position in the fuel tank.
Some tank closure valves of the type used in tank venting control systems also have a tendency to remain "stuck" in their closed positions. This sticking can prolong the closure of the venting outlet in the fuel tank. Such closure can continue during high tank pressure conditions for a period of time after the liquid fuel level in the tank has fallen far enough so the float member and tank closure member would ordinarily "fall" in the tank away from the venting outlet. The prolonged closure of the closure valves often occurs because of a high-pressure differential that acts on such tank closure valves. This is especially evident when the venting outlet in the fuel tank has a relatively large inner diameter. What is needed is tank venting control apparatus that includes a float member that jerks to a closed position when exposed to rapidly rising liquid fuel during sloshing conditions, but relies primarily on buoyancy during normal refueling conditions. What is also needed is a fill-limit valve assembly that includes a closure valve that falls away from the venting outlet when the liquid fuel in the tank has lowered in the fuel tank.
According to the present invention an apparatus is provided for controlling discharge of fuel vapor from within a vehicle fuel tank. The apparatus comprises a valve container adapted to be mounted in a top wall of the fuel tank and a valve member. The valve container is formed to include an inlet in fluid communication with the fuel tank, an outlet, a side wall extending between the inlet and outlet, and a chamber in fluid communication with the inlet and the outlet. The valve member is disposed in the chamber and formed for movement between an open position allowing flow of fuel vapor through the outlet and a closed position preventing flow of fuel vapor through the outlet. The valve member includes a central post and wing segments positioned to lie in a spaced apart relationship about the post. The wing segments are formed to define flow passages therethrough that are sized to permit the flow of fuel vapor therethrough and to momentarily block the flow of liquid fuel therethrough.
According to another embodiment of the present invention, a fuel vapor control valve is provided for controlling the flow of fuel vapor and liquid fuel through an aperture in a fuel tank having a filler neck. The fuel vapor control valve comprises a housing mounted in the aperture and formed to include an inlet in fluid communication with the fuel tank, an outlet, a side wall extending between the inlet and the outlet and defining a chamber disposed between the inlet and the outlet. Control valve also includes a base coupled to the side wall of the housing and being formed to include a slot therethrough, an upper closure member configured for selectively interrupting the flow of fuel vapor through the outlet, and a valve member formed for movement in the chamber between the outlet and the base. The valve member includes a post movably coupled to the closure member and a wing segment coupled to the post. The wing segment defines a flow passage that is sized to permit the flow of fuel vapor therethrough and to retard the flow of liquid fuel therethrough.
According to yet another embodiment of the present invention a float member is provided that is suitable for use in a tank venting control system for regulating discharge of fuel vapor from within a vehicle fuel tank. The float member comprises a central post that has an upper end and an opposite lower end and is formed to define a cavity between the upper and lower ends. A dome portion is coupled to the central post and is configured to extend across the cavity adjacent the upper end. Further, float valve includes wing segments positioned to lie in a spaced apart relationship about an outer circumference of the central post. Each of the wing segments includes an exterior wall and an opposite interior wall coupled to the central post. The exterior and interior walls cooperate to define a flow passage therebetween. In addition, the flow passage permits fuel vapor to flow freely therethrough and retards liquid fuel flow therethrough.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of the preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.